This review discusses the electrochemical principles involved in the recovery of metals from aqueous solutions and fused salt electrolytes. In this article we concentrate on electrolytic processing of different types of metals with an emphasis on the significant role of electrochemical principles together with free energy and activity in electrowinning and electrorefining of common and reactive metals. Based on discharge potentials, metals are classified into three categories with respect to their characteristics of deposition from aqueous electrolytes without hydrogen evolution, under hydrogen over-voltage, and only from fused electrolytes.
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